A device for transferring heavy loads at sea is disclosed in U.S. Pat. No. 3,945,508 where a device for connecting two ships employs an inverted V-shaped cargo boom having one leg mounted on each ship. With such arrangement, however, transfers can only occur during periods of calm seas.
U.S. Pat. Nos. 3,428,194 and 4,027,800 are both directed to marine gantry cranes for handling carbon aboard ship while U.S. Pat. No. 3,757,678 is directed to a marine crane for handling logs. None of these patents deals with connecting two bodies to compensate for relative movement caused by wave motion.
A combined marine ramp transfer and mooring system is illustrated and described in U.S. Pat. No. 4,003,473. The ramp connects the two vessels so that personnel and/or material can travel between the two.
Trolley-type, high-line, transfer systems between ships are taught in U.S. Pat. Nos. 3,012,518 and 3,787,031 where a high-line cable is connected between ships so that cargo can be transferred.
Motion compensation systems for cranes and other cargo transfer equipment mounted on a vessel have been developed. In U.S. Pat. No. 4,021,019 a heave compensated crane is disclosed for holding a load at a fixed position and in U.S. Pat. No. 3,916,811 a tide compensation system for a vessel is disclosed.
Marine crane motion compensation systems are the subject of U.S. Pat. Nos. 3,591,022; 3,662,991; and 4,126,298 where under rough sea conditions a line connected to the cargo carrying surface of the other vessel in addition to a load carrying line ensures non-impact and precise placement of the cargo. Such a system can be supplemented with means to ensure that the cargo is lifted from the vessel at the wave crest of the relative motion cycle as disclosed in U.S. Pat. No. 4,025,055. Another motion compensator is taught in U.S. Pat. No. 4,174,188 where a supplemental cargo support is mounted on the deck of a vessel and is raised or lowered at an appropriate time for compensating for wave motion.